A pump, which is a device for transporting a fluid such as water, has been developed so as to transport a cooling liquid for a heat generating element, typically represented by a CPU, to transport blood to a blood inspecting chip, to apply a fine amount of medicine to the human body, to provide a Lab on a chip that can downsize chemical experiments or chemical operations so as to be integrated, or to supply a fuel such as methanol to a fuel battery. In these applications, small-size, light-weight, low-voltage and noiseless devices are required. In order to meet these demands, for example, a pump using a conductive polymer film has been proposed (for example, Patent Document 1). In general, an actuator using a conductive polymer film is characterized by advantages, such as light weight, a low voltage and noiseless operations.
FIGS. 48A to 48C show a pump structure of a diaphragm system proposed in Patent Document 1.
The pump shown in FIG. 48A is provided with diaphragms 403 and 404 respectively made of conductive polymer films, which are placed inside of a casing unit 402. The diaphragm 403 is defined as the first diaphragm, and the diaphragm 404 is defined as the second diaphragm. The casing unit 402 has a cylindrical shape, with an inner space. The first and second diaphragms 403 and 404 are respectively prepared as disc-shaped conductive polymer films, and have their respective peripheral portions secured to the casing unit 402 at securing portions 430 and 431. Moreover, the first and second diaphragms 403 and 404 are mutually connected to each other by a connecting member 406 at their respective center portions. In this manner, the first and second diaphragms 403 and 404 are installed, with tensions being applied in the respective film face directions, so as to respectively form cone shapes. In this structure, a ring-shaped space portion 409, surrounded by the first and second diaphragms 403 and 404 and the casing unit 402, is defined as an electrolyte chamber. The electrolyte chamber is filled with an electrolyte. The first and second diaphragms 403 and 404 are connected to a power supply 410c through respective lead lines 410a and 410b. By applying voltages having mutually reversed phases to the first and second diaphragms 403 and 404 respectively, the respective conductive polymer films of the first and second diaphragms 403 and 404 carry out expanding and contracting movements. Now, a first space portion 407 surrounded by the casing unit 402 and the first diaphragm 403 is referred to as a first pump chamber, and a second space portion 408 surrounded by the casing unit 402 and the second diaphragm 404 is referred to as a second pump chamber. In a state shown in FIG. 48A, the first diaphragm 403 is expanded, and the second diaphragm 404 is contracted. In this state, a liquid outside the first pump chamber 407 is sucked to the inside of the first pump chamber 407 from a first inlet 411a provided with a first inlet valve 412, and a liquid inside the second pump chamber 408 is discharged outside the second pump chamber 408 from a second outlet 413b provided with a second outlet valve 424. Moreover, in contrast, in a state where the first diaphragm 403 is contracted and the second diaphragm 404 is expanded, a liquid outside the second pump chamber 408 is sucked to the inside of the second pump chamber 408 from a second inlet 411b provided with a second inlet valve 423, and a liquid inside the first pump chamber 407 is discharged outside the first pump chamber 407 from a first outlet 413a provided with a first outlet valve 422. By continuously carrying out the switching between these two states, the increase and reduction of the volume of each of the first pump chamber 407 and the second pump chamber 408 are repeated so that the corresponding suction and discharge of the fluid to the respective pump chambers are repeated. With this arrangement, the pump functions are carried out. In a state in which the first and second diaphragms 403 and 404 are slackened, since a force of electrochemomechanical expansion or contraction of the conductive polymer film is not transmitted to the fluid inside the pump chamber, but released to escape, with the result that the operating efficiency of the pump is lowered. Therefore, it is necessary to keep the first diaphragm 403 and the second diaphragm 404 in the expanded state respectively without being slackened; however, in the pump of FIG. 48A, by making the pressure of the electrolyte inside the electrolyte chamber 409 smaller than the pressure of each of the fluids in the first pump chamber and the second pump chamber, the first diaphragm 403 and the second diaphragm 404 can be kept in an expanded state without being slackened respectively.
Moreover, a pump shown in FIG. 48B, which has virtually the same structure as that of the pump of FIG. 48A, is different therefrom in that no connecting member 406 is installed. In the present structure, the first and second diaphragms 403 and 404 exert forces to each other through an electrolyte filled in the space portion 409. With this arrangement, the same operations as those of FIG. 48A can be carried out. In the pump of FIG. 48B, by making the pressure of the electrolyte inside the electrolyte chamber 409 greater than the pressure of each of the fluid inside the first pump chamber and the fluid inside the second pump chamber, or smaller than the pressure thereof, the first diaphragm 403 and the second diaphragm 404 can be kept in an expanded state without being slackened respectively.
Moreover, in the pump of FIG. 48C, only one diaphragm 403 made of a conductive polymer film is formed inside the casing unit 402. The casing unit 402 has a cylindrical shape, with an inner space formed therein. The diaphragm 403 is a disc-shaped conductive polymer film, and has its peripheral portion secured to the casing unit 402 at a securing portion 430. Furthermore, the diaphragm 403 is connected to the casing unit 402 by a spring member 451. The diaphragm 403 is disposed with a tension being applied in the film face direction, and formed into a cone shape. In FIG. 48C, a space portion 409, located below the diaphragm 403 and surrounded by the diaphragm 403 and the casing unit 402, is defined as an electrolyte chamber. The electrolyte chamber 409 is filled with an electrolyte. The diaphragm 403 and an electrode 450 are respectively connected to a power supply 410c through lead lines 410a and 410b. A space portion 407 surrounded by the diaphragm 403 and the casing unit 402 is defined as a pump chamber. By applying voltages having mutually reversed phases to the diaphragm 403 and the electrode 450, the conductive polymer film of the diaphragm 403 carries out expanding and contracting movements. In a state shown in FIG. 48C, the diaphragm 403 is kept in an expanded state. In this state, a liquid outside the pump chamber 407 is sucked to the inside of the pump chamber 407 from an inlet 411 provided with an inlet valve 412. In contrast, in a state where the diaphragm 403 is contracted, a liquid inside the pump chamber 407 is discharged outside of the pump chamber 407 from the outlet 413 provided with an outlet valve 422. By continuously carrying out the switching between these states, the increase and reduction of the volume of the pump chamber 407 are repeated so that the corresponding suction and discharge of the fluid are repeated. With this arrangement, the pump functions are carried out.